Differences in Phytosiderophore Production of Grain Sorghum Cultivars.

Grain sorghum (Sorghum bicolor) is especially susceptible to iron deficiency chlorosis when grown in high pH soils in the Great Plains. This study was conducted in order to develop a high throughput protocol for screening sorghum varieties for IDC tolerance to assist in future breeding of IDC tolerant grain sorghum varieties. A hydroponics system will be developed to screen sorghum for tolerance to IDC and phytosiderophore production. The hydroponics system that will be used in this study will model the methods used by Erenoglu et al. (2000), which examined IDC in barley. During protocol development four sorghum hybrids will be used that have shown tolerance or susceptibility to IDC under field conditions in western Kansas. Seeds will be germinated in silicon sand, then transferred to 3 gallon vessels containing 3 L of nutrient solution under controlled greenhouse conditions at the KSU Throckmorton Plant Sciences Center in Manhattan, KS. The nutrient solution will be sprayed over the roots continuously using a submerged pump. Each hydroponics container will contain two seedlings of the same sorghum line in order to increase total root biomass in the container, and thus the PS quantity in the wash solution at the time of collection. The nutrient solution will be composed of: 0.88 mM K2SO4, 2 mM Ca(NO3)2, 0.25 mM KH2PO4, 1.0 mM MgSO4, 0.1 mM KCl, 1 μM H3BO3, 1 μM ZnSO4, 0.5 μM MnSO4, 0.2 μM CuSO4, and 0.02 μM (NH4)6MoO24; and will be created using high grade reagents to avoid Fe contamination. Three repetitions will be conducted in Mar.-Apr. Because sorghum exhibits IDC symptoms immediately following germination indicating IDC tolerance or susceptibility, seedling plants will be used in order to minimize greenhouse space and nutrient solution volume requirements. The extent to which a plant is exhibiting IDC will be determined using the scoring system method described in the preliminary study. In addition, relative leaf chlorophyll content will be determined using SPAD 502 chlorophyll meter (Minolta, Corp., Tokyo, Japan). Data is currently being collected and analyzed.